NEW YORK — Accuse Representative Seth Moulton of loving trains too much at your peril. Yes, the Massachusetts Democrat worked for a time on a high-speed-rail project in Texas, one that is now finally inching toward a groundbreaking ceremony. He’s pressed for a new rail tunnel in Boston. He’s a booster for commuter rail. But ask him why he loves trains, and he’ll correct you, firmly. “It's not that I just like trains so much,” he says. “We should have a transportation system that’s balanced and gives people options.”